Cycles: pointcloud rendering

This add support for rendering of the point cloud object in Blender, as a native
geometry type in Cycles that is more memory and time efficient than instancing
sphere meshes. This can be useful for rendering sand, water splashes, particles,
motion graphics, etc.

Points are currently always rendered as spheres, with backface culling. More
shapes are likely to be added later, but this is the most important one and can
be customized with shaders.

For CPU rendering the Embree primitive is used, for GPU there is our own
intersection code. Motion blur is suppored. Volumes inside points are not
currently supported.

Implemented with help from:
* Kévin Dietrich: Alembic procedural integration
* Patrick Mourse: OptiX integration
* Josh Whelchel: update for cycles-x changes

Ref T92573

Differential Revision: https://developer.blender.org/D9887

1 files changed, 28 insertions, 0 deletions

diff --git a/intern/cycles/kernel/bvh/traversal.h b/intern/cycles/kernel/bvh/traversal.h
index 1c17ebf767f..180f19d11c5 100644
--- a/intern/cycles/kernel/bvh/traversal.h
+++ b/intern/cycles/kernel/bvh/traversal.h
@@ -28,6 +28,7 @@
  * without new features slowing things down.
  *
  * BVH_HAIR: hair curve rendering
+ * BVH_POINTCLOUD: point cloud rendering
  * BVH_MOTION: motion blur rendering
  */
 
@@ -188,6 +189,33 @@ ccl_device_noinline bool BVH_FUNCTION_FULL_NAME(BVH)(KernelGlobals kg,
               break;
             }
 #endif /* BVH_FEATURE(BVH_HAIR) */
+#if BVH_FEATURE(BVH_POINTCLOUD)
+            case PRIMITIVE_POINT:
+            case PRIMITIVE_MOTION_POINT: {
+              for (; prim_addr < prim_addr2; prim_addr++) {
+                if ((type & PRIMITIVE_ALL_MOTION) && kernel_data.bvh.use_bvh_steps) {
+                  const float2 prim_time = kernel_tex_fetch(__prim_time, prim_addr);
+                  if (ray->time < prim_time.x || ray->time > prim_time.y) {
+                    continue;
+                  }
+                }
+
+                const int point_object = (object == OBJECT_NONE) ?
+                                             kernel_tex_fetch(__prim_object, prim_addr) :
+                                             object;
+                const int point_prim = kernel_tex_fetch(__prim_index, prim_addr);
+                const int point_type = kernel_tex_fetch(__prim_type, prim_addr);
+                const bool hit = point_intersect(
+                    kg, isect, P, dir, isect->t, point_object, point_prim, ray->time, point_type);
+                if (hit) {
+                  /* shadow ray early termination */
+                  if (visibility & PATH_RAY_SHADOW_OPAQUE)
+                    return true;
+                }
+              }
+              break;
+            }
+#endif /* BVH_FEATURE(BVH_POINTCLOUD) */
           }
         }
         else {